在PySpark本地模式下，无法加载25GB数据集，RAM为56GB。

Question

我在加载和处理25GB镶木地板数据集（共个）时遇到问题stackoverflow.com网站posts）在本地模式下的一台beefy机器上（12核/64GB RAM）。

我的机器上有更多的空闲内存并分配给pyspark，这比拼花数据集的大小还要多（更不用说数据集的两列了），但是一旦加载数据帧，我就无法对其运行任何操作。这太令人困惑了，我不知道该怎么办。在

具体来说，我有一个25GB的拼花地板数据集：

$ du -sh data/stackoverflow/parquet/Posts.df.parquet

25G data/stackoverflow/parquet/Posts.df.parquet

我有一台有56GB可用内存的机器：

^{pr2}$

我已经将PySpark配置为使用50GB的RAM（尝试调整maxResultSize，但没有效果）。在

我的配置如下：

$ cat ~/spark/conf/spark-defaults.conf

spark.io.compression.codec org.apache.spark.io.SnappyCompressionCodec
spark.driver.memory 50g
spark.jars ...
spark.executor.cores 12
spark.driver.maxResultSize 20g

我的环境是这样的：

$ cat ~/spark/conf/spark-env.sh

PYSPARK_PYTHON=python3
PYSPARK_DRIVER_PYTHON=python3
SPARK_WORKER_DIR=/nvm/spark/work
SPARK_LOCAL_DIRS=/nvm/spark/local
SPARK_WORKER_MEMORY=50g
SPARK_WORKER_CORES=12

我这样加载数据：

$ pyspark

>>> posts = spark.read.parquet('data/stackoverflow/parquet/Posts.df.parquet')

它加载正常，但是任何操作（包括我首先对数据帧运行limit(10)）都会导致堆空间不足错误。在

>>> posts.limit(10)\
    .select('_ParentId','_Body')\
    .filter(posts._ParentId == 9915705)\
    .show()

[Stage 1:>                                                       (0 + 12) / 195]19/06/30 17:26:13 ERROR Executor: Exception in task 7.0 in stage 1.0 (TID 8)
java.lang.OutOfMemoryError: Java heap space
19/06/30 17:26:13 ERROR Executor: Exception in task 3.0 in stage 1.0 (TID 4)
java.lang.OutOfMemoryError: Java heap space
19/06/30 17:26:13 ERROR Executor: Exception in task 5.0 in stage 1.0 (TID 6)
java.lang.OutOfMemoryError: Java heap space
at java.nio.HeapByteBuffer.<init>(HeapByteBuffer.java:57)
at java.nio.ByteBuffer.allocate(ByteBuffer.java:335)
at org.apache.parquet.bytes.HeapByteBufferAllocator.allocate(HeapByteBufferAllocator.java:32)
at org.apache.parquet.hadoop.ParquetFileReader$ConsecutiveChunkList.readAll(ParquetFileReader.java:1166)
at org.apache.parquet.hadoop.ParquetFileReader.readNextRowGroup(ParquetFileReader.java:805)
at org.apache.spark.sql.execution.datasources.parquet.VectorizedParquetRecordReader.checkEndOfRowGroup(VectorizedParquetRecordReader.java:301)
at org.apache.spark.sql.execution.datasources.parquet.VectorizedParquetRecordReader.nextBatch(VectorizedParquetRecordReader.java:256)
at org.apache.spark.sql.execution.datasources.parquet.VectorizedParquetRecordReader.nextKeyValue(VectorizedParquetRecordReader.java:159)
at org.apache.spark.sql.execution.datasources.RecordReaderIterator.hasNext(RecordReaderIterator.scala:39)
at org.apache.spark.sql.execution.datasources.FileScanRDD$$anon$1.hasNext(FileScanRDD.scala:101)
at org.apache.spark.sql.execution.datasources.FileScanRDD$$anon$1.nextIterator(FileScanRDD.scala:181)
at org.apache.spark.sql.execution.datasources.FileScanRDD$$anon$1.hasNext(FileScanRDD.scala:101)
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.scan_nextBatch_0$(Unknown Source)
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.processNext(Unknown Source)
at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(BufferedRowIterator.java:43)
at org.apache.spark.sql.execution.WholeStageCodegenExec$$anonfun$13$$anon$1.hasNext(WholeStageCodegenExec.scala:636)
at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:409)
at org.apache.spark.shuffle.sort.BypassMergeSortShuffleWriter.write(BypassMergeSortShuffleWriter.java:125)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:55)
at org.apache.spark.scheduler.Task.run(Task.scala:121)
at org.apache.spark.executor.Executor$TaskRunner$$anonfun$10.apply(Executor.scala:408)
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1360)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:414)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
19/06/30 17:26:13 ERROR Executor: Exception in task 10.0 in stage 1.0 (TID 11)
java.lang.OutOfMemoryError: Java heap space
    at java.nio.HeapByteBuffer.<init>(HeapByteBuffer.java:57)
    at java.nio.ByteBuffer.allocate(ByteBuffer.java:335)
    at org.apache.parquet.bytes.HeapByteBufferAllocator.allocate(HeapByteBufferAllocator.java:32)
    at org.apache.parquet.hadoop.ParquetFileReader$ConsecutiveChunkList.readAll(ParquetFileReader.java:1166)
    at org.apache.parquet.hadoop.ParquetFileReader.readNextRowGroup(ParquetFileReader.java:805)
    at org.apache.spark.sql.execution.datasources.parquet.VectorizedParquetRecordReader.checkEndOfRowGroup(VectorizedParquetRecordReader.java:301)
    at org.apache.spark.sql.execution.datasources.parquet.VectorizedParquetRecordReader.nextBatch(VectorizedParquetRecordReader.java:256)
    at org.apache.spark.sql.execution.datasources.parquet.VectorizedParquetRecordReader.nextKeyValue(VectorizedParquetRecordReader.java:159)
    at org.apache.spark.sql.execution.datasources.RecordReaderIterator.hasNext(RecordReaderIterator.scala:39)
    at org.apache.spark.sql.execution.datasources.FileScanRDD$$anon$1.hasNext(FileScanRDD.scala:101)
    at org.apache.spark.sql.execution.datasources.FileScanRDD$$anon$1.nextIterator(FileScanRDD.scala:181)
    at org.apache.spark.sql.execution.datasources.FileScanRDD$$anon$1.hasNext(FileScanRDD.scala:101)
    at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.scan_nextBatch_0$(Unknown Source)
    at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.processNext(Unknown Source)
    at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(BufferedRowIterator.java:43)
    at org.apache.spark.sql.execution.WholeStageCodegenExec$$anonfun$13$$anon$1.hasNext(WholeStageCodegenExec.scala:636)
    at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:409)
    at org.apache.spark.shuffle.sort.BypassMergeSortShuffleWriter.write(BypassMergeSortShuffleWriter.java:125)
    at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99)
    at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:55)
    at org.apache.spark.scheduler.Task.run(Task.scala:121)
    at org.apache.spark.executor.Executor$TaskRunner$$anonfun$10.apply(Executor.scala:408)
    at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1360)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:414)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
19/06/30 17:26:13 ERROR Executor: Exception in task 6.0 in stage 1.0 (TID 7)
java.lang.OutOfMemoryError: Java heap space
19/06/30 17:26:13 ERROR SparkUncaughtExceptionHandler: Uncaught exception in thread Thread[Executor task launch worker for task 7,5,main]
java.lang.OutOfMemoryError: Java heap space
19/06/30 17:26:13 ERROR SparkUncaughtExceptionHandler: Uncaught exception in thread Thread[Executor task launch worker for task 11,5,main]
java.lang.OutOfMemoryError: Java heap space
...

下面将运行，表明问题出在_Body字段（显然是最大的）：

>>> posts.limit(10).select('_Id').show()

+---+
|_Id|
+---+
|  4|
|  6|
|  7|
|  9|
| 11|
| 12|
| 13|
| 14|
| 16|
| 17|
+---+

我该怎么办？我可以使用EMR，但我希望能够在本地加载此数据集，在这种情况下，这样做似乎是完全合理的。在

Answer 1

Spark的存储和计算的默认内存部分是0.6。在您的配置下，它将是0.6 * 50GB = 30GB。但是，在内存中表示数据可能会比序列化的磁盘版本消耗更多的空间。在

请查看Memory Management部分以获取更多详细信息。在